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Nrrn rares 1 JOHN S. STONE, OEBOSTON, MASSACHUSETTS,- ASSIGNOR TO THE AMERICAN BELL TELEPHONE COMPANY, OF SAME PLACE.

TELEPHONEQCIRCUIT.

SPECIFICATION forming part of Letters ippiicaion ned March 13, i896.

.T0 a/ZZ whom t may concern,.-

Be it known that I, JOHN S. STONE, residing at Boston, in the county of Suffolk and State of Massachusetts, have invented certain Im* provements in Telephone-Circuits, of which the following isa specification.

This inventionrelates to multiple common battery switchboards, and particularly to the means for signaling, testing, and conversation. Itis associated with the type of switchboards which are provided with open-ter1ni nal spring-jacks on each section and inwhich incandescent lamps are employed for the line and clearing-out signals. The substations are provided with the usual instruments employed in common battery systemsi. c., a high resistance callbell in a permanent bridge, a receiving and `transmitting telephone, and a hook-switch. A common generator for operating the signal-circuit and for energizing the substation telephone-transmitters is located between the coils of a relay and in apermanent bridge between the line conductors of each substation-circuit. The relay-armature operates to close and open a combined signal and test circuit, which is grounded at one end through a resistance and at the other end through a line lamp-signal and battery, there being branch connections to the test-contacts of each spring-jack. The coils of the relay act as impedances. The operators cord-circuits are conductively divided, but inductively united by a repeatingcoil, and a clearing-out or disconnecting lampsignal is located in each plugcircuit in a branch connection extending from a metal ring on the plug todthe conductor of the sig nalin g and test circuit. When a call is made from a substation, the common generator energizes the relay-coils and the armature closes thesignaling-circuit, the line lamp-signal is supplied with energy from the battery in the said circuit, and is lighted. The insertion of the answering-plug in the line-socket brings the metal ring thereof into engagement with the test-contact piece of the socket, thereby bringing the `disconnecting lamp-signal into parallel circuit i with the line-signal. The current in the signaling-circuit is approXi mately constant, owing to the resistance therein, and consequently the two lamp-signals Patent No. 560,761, dated May 26, 1896.

Serial No. 583,113. (No model.)

shunt each other to such an extent as to eX- tinguish the line-signal and prevent the disconnecting-signal from lighting; but the relayarmature remains attracted to its cores. The testing is done in the usual way. `When two substatioircircuits are looped together, each circuit is thus provided with a battery for signaling and conversation purposes, and the impedances oneach side thereof prevent the sound-waves from being short-circuited therethrough. Vhen two substation-circuits are of the same or of approximate resistance, the same battery may be connected to both; but if they are of `widely-varying resistance two separate batteries are employed.

In the drawings which form part of this specification, Figure l is a diagram illustrating the invention, showing two substation- :circuits in association with an operators cordcircuit; and Fig. 2 is a diagram showing schematically two substations looped together for conversation. 7

X and Z represent the substations, and Y the central station.

B is the high-resistance bell in a bridge l between the line conductors d and b, which are adapted for connection with telephones tand T, the former being shown upon the hook-switch s, so that the branch through the saidV telephones is normally open.

J J2 are branch terminal-plug sockets or jacks upon the switchboard-sections.

i A is a relay, whose coils 3 and e are in the bridge 5 between the conductors a and b, the generator B2 being interposed between the said coils. The relay-armature tu controls the combined signal and test circuit 7, from which branches lO extend to the test-rings 11.

'O ne end or side of the circuit is grounded through the resistance c. The opposite end' or side serially includes the line lamp-signal m and is grounded through the battery O.

The operators cord-circuits are inductively united by the repeating-coil l, the windings terminating in the tip d and sleeve c of the plugs l? and P2, respectively. The windings are of sufiicient resistance to prevent the operation of the relay when the cord-plug is in a spring-jack andthe substation-circuit is open at its hook-switch- There is a disconnecting lam p-si gnal in each IOO plug-circuit, which is included in a branch conductor f, connecting a metal ring r on each plug with the signal and test circuit conductor at point' 13.

The operators apparatus is the same as usual, and only the receiving-telephone t2 in circuit with the condenser and grounded at the center of its coil through a resistance 17 is shown.

In the operation of the invention, when the telephone t is removed from its hook-switch and the circuit is closed,the current ofthe generator B2 energizes the relay A, and its armature closes the normally open signal-circuit 7, permitting current from battery C to iiow therein and to light the lamp m.

When the answering-plug vP is inserted in the socket of jack J, its tip makes contact with the upper spring thereof and its sleeve with the lower spring. At the same time the ring r engages the test-contact piece 11, making a circuit from ground G, resistance c, branch 10, by wires f and 7 and 12, battery C to ground G2, thereby placing the disconnccting lamp-signal in parallel with the line lamp-signal, and as the current from the battery C is substantially constant, owing to the presence of resistance c, the two lamps shunt each other, and the line lamp-signal is eX- tinguished. There is, however, suiiicient current through the relay A to hold the armature u: attracted.

The test is made in the usual way by touching the test-contact 11 of the circuit wanted with the tip of the calling-plug P2. If the line is busy, there will be a circuit from ground G3, wire 16, telephone t2, tip d of plug P2, ring 11, branch lO, wires '7 and 12, battery C to ground G2, and the usual click will be heard in the telephone t2 due to the charging of the condenser by the battery. If the line is not busy, no circuit is formed and the plug is inserted in the socket of the line.

When the telephone at each substation is returned to its hook-switch, the circuit is thereby opened and the armature w falls back, opening the signal-circuit, whereupon the whole current from battery C passes through the circuit previously described and lights the disconnecting lamp-signal g, and upon the withdrawal of the plugs P the lamps are eX- tin guished.

Fig. 2 illustrates two substation-circuits looped together for conversation. Each circuit is represented by a battery B2 B3 in a bridge between the circuit-conductors, which may be the same, or a separate battery with the relay impedance-coils 3 and 4 on each side thereof, and each circuit repeating into the other by means of the repeating-coil I. Vires 50 50 and 60 (30 from the poles of the batteries indicate that these batteries are common to other circuits.

By the use of separate generators in cach substation circuit conversation circuits of varying resistances can be better served and the use of a condenser in the cord-circuit, which heretofore 'has been requisite, is avoided, and by means of the relay A, operated by the said generator,` the operation of the line and disconnecting lamp-signals are distinctly individualized, so that the signals in one circuit are not disturbed by the manipulations taking place in other circuits.

Having now fully described my invention, I claim- 1. The combination with a telephone-circuit, of a generator and a relay in a permanent bridge between the circuit-conductors, the generator being interposed between the coils of the relay; and a local circuit including a battery, a line lamp-sign al controlled by the relay, and means for shunting the signal when connection is made with the line, as set forth.

2. The combination with a telephone-circuit provided with means at the substation for closing the circuit, of a generator and relay in a permanent bridge between the circuitconductors,the generator being interposed between the coils of the relay; and a local circuit including a battery, and a line lamp-signal controlled by the relay, and means for 'shunting and extinguishing the signal when connection is made with the line as set forth.

3. The combination with a telephone-circuit provided with means at the substation for closing the circuit, of a generator and a relay in a permanent bridge between the circuitconductors the generator being interposed between the coils of the relay; a normally open local circuit grounded at both ends adapted to be closed by the relay; test-contacts in openterminal spring-jacks and branches from the contacts to the local circuit; whereby when the circuit is closed at the substation the electrical condition of the test-contacts is changed as set forth.

4. The combination with a telephone-circuit provided with means at the substation for closing the circuit; of a generator and a relay in a permanent bridge between the circuitconductors,th e generator being interposed between the coils of the relay; a normally open local circuit including a resistance, a battery, and a line lamp-signal controlled by the relay; test-contacts in open-terminal springjacks having branch connections to the local circuit; and a plug provided with a contactring connected to a disconnecting lamp-signal and to the local circuit; whereby when the plug is inserted in a jack the line lamp-signal is extinguished, and the electrical condition of the test-contacts is changed, as set forth.

5. The combination of two telephone-circuits looped together for conversation by plugs and cords which are inductively united by the two windings of a repeating-coil; each circuit having in a permanent bridge between its conductors a generator and a relay whose helices serve as impedances; a local circuit closed by the said relay; and a shunted disconnecting lamp-signal in cach plug-circuit;

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-whereby upon the opening of either circuit at contacts; whereby when both branches are closed, the disconnecting-signal may be set when in response to the substation circuitchanger4 the relay branch contacts are separated, substantially as specified.

In testimony whereof I have signed my name to this specication, in the presence of two subscribing witnesses, this 7th day of March, 1896. t

JOHN S. STONE.

Witnesses:

GEO. WILLIS PIERCE, JOSEPH A. GATELY. 

